1. Field of the Invention
The present invention relates to a system and method of determining properties of a semiconductor resistance device, and more particularly, to a system and method of determining pulse properties of a semiconductor resistance device.
2. Description of the Related Art
Methods of determining the operating properties or estimating the reliability of semiconductor resistance devices have been researched. For example, methods of determining resistance and current changes in a resistance random-access memory (RRAM), which stores data bits using resistance changes, and in a resistance switch have been researched. A phase change random-access memory (PRAM), a magnetic random-access memory (MRAM), an oxide random-access memory (OxRAM), etc. are all types of RRAMs whose resistances can be dynamically changed with respect to changes in an applied electric signal. Examples of the resistance switch are a CuS switch, which uses migration of CuS, and a chalcogenide switch, which uses a chalcogenide material like GeSbSe.
High-speed semiconductor resistance devices need to determine properties corresponding to high frequency signals in RRAMs and also corresponding to resistance switches. For example, the high frequency pulse properties of RRAM can be determined using a high frequency pulse generator. The pulse properties are, for example, resistance and current properties.
FIGS. 1 through 3 illustrate the results of determining the properties of a PRAM using a pulse voltage generator and a current-voltage meter. FIG. 1 is a graph showing program resistances with respect to various pulse voltages, which are determined by a conventional method of determining properties of a resistance memory device. FIG. 2 is a graph showing relations of direct current (DC) currents versus DC voltages determined using a current-voltage meter according to a conventional method of determining properties of a resistance memory device. Changes in resistance (hereinafter, referred to as a program resistance Rp) with respect to a pulse voltage (Vp) after operating a set or reset program are shown in FIG. 1. A threshold voltage and reset current of a PRAM can be determined based on the results shown in FIG. 1. To obtain a program resistance Rp of a PRAM, it is necessary to perform a two-step operation, such as applying a pulse voltage Vp and applying a direct current (DC) voltage VD, which is used to determine DC current ID, as shown in FIG. 2.
FIG. 3 is a graph illustrating program resistance changes of a resistance memory device, which are caused by applying a DC current according to a conventional method of determining properties of a resistance memory device. When a pulse voltage and a DC voltage are alternately applied on a PRAM using one apparatus, a switch device, for example, a radio frequency (RF) switch, is necessary, and thus a pulse current Ip flowing in the PRAM cannot be simultaneously determined while applying a pulse voltage Vp. A current-voltage meter should be used for determining a reset current of the PRAM, and thus a high voltage (for example, about 2 V) that is greater than a threshold voltage of the PRAM should be applied to the PRAM. Here, the PRAM is stressed by the applied high voltage and damaged, resulting in a significant change in the relationship between the pulse current and the program resistance Rp. The results based on the first measurement (●) and the second measurement (□) are shown in FIG. 3, and the results of each measurement show a significant difference in the relationships between the program resistance Rp and the pulse current Ip.
In addition, the resistance of the PRAM while applying a pulse voltage (referred to as a dynamic resistance Rd) cannot be determined. That is, a dynamic change in an interface between a phase change film and a lower electrode is unknown during PRAM operations.